1. Field of the Invention
The invention concerns a process for the preparation of a definite shape of cross-linked synthetic plastic materials including tubular shapes. The plastics utilized include, in particular, polyethylene in its many forms such as low density polyethylene (LDPE), medium density polyethylene (MDPE), and (HDPE) high density polyethylene, polymethacrylate (PMMA), polyvinylacetate (PVA), polymethylacrylate (PMMA), polyvinylchloride (PVC) and ethylenevinylacetate (EVA).
2. Background of the Prior Art:
Synthetic products and in particular synthetic plastic tubing are being used increasingly, for example, in the field of heating and sanitation. These materials have outstanding long term stability even at high temperatures and pressures and are resistant to most of the substances that are utilized or added to heating and sanitation systems. If, for example, the tubing is exposed to extreme bending during installation, in order perhaps to be built into an assembly after being equipped with fittings, the pipes must be fastened and possibly cast in the bent state as relatively strong restoring forces are present in the pipes and tubing and are highly resistant to extreme bending. If a pipe of this type is subjected to angling, for example, a kinking location with a reduced cross section is formed resulting in an area of increased resistance to flow.
Certain subsequent deformations of the molded material cannot be effected without residual stresses, other deformations can be effected only with great difficulty.